Device and method for the creation of a circumferential cryogenic lesion in a pulmonary vein

ABSTRACT

A device and method for ablating tissue includes a sheath system with an occlusion structure. In certain embodiments, arrhythmias originating in pulmonary veins are treated cryogenically.

INCORPORATION BY REFERENCE

[0001] The entire disclosures of each of U.S. Pat. No. 6,035,657, issuedMar. 14, 2000 for a FLEXIBLE CATHETER CRYOSURGICAL SYSTEM (“the '657patent”), U.S. Pat. No. 5,910,104 issued Jun. 8, 1999 for a CRYOSURGICALPROBE WITH DISPOSABLE SHEATH (“the '104 patent”) and U.S. Pat. No.5,275,595 issued Jan. 4, 1994 for a CRYOSURGICAL INSTRUMENT (“the 595patent”), all assigned to CryoGen, Inc. of San Diego, Calif. are herebyexpressly incorporated by reference in their entireties.

FIELD OF THE INVENTION

[0002] The present invention relates generally to devices and methodsfor the treatment of cardiac arrhythmia and more specifically relates todevices and methods for the treatment of focal atrial arrhythmia.

BACKGROUND INFORMATION

[0003] Cardiac rhythm is maintained by precisely timed nerve signalselectrically exciting and being conducted through cardiac tissue tostimulate synchronous contractions of the four heart chambers (2ventricles and 2 atria). In a normal sinus rhythm, the nerve signals aretypically conducted along paths initiating at the sino-atrial (SA) nodeand passing from there through the atrioventricular (AV) node and thebundle of His to the ventricular myocardial tissue.

[0004] Potentially dangerous abnormal cardiac rhythms, or arrhythmias,including atrial fibrillation, are common medical conditions which mayresult from disturbances in the site of origin and/or the pathways ofconduction of the nerve signals exciting contraction of the fourchambers of the heart. The site of origin and pathways of conduction ofthese signals are currently mapped, for example using anelectrocardiograph (ECG) in conjunction with mapping methods such asthose described in U.S. Pat. No. 4,641,649 to Walinsky et al.

[0005] One common type of atrial fibrillation occurs when thecontraction initiating signals originate within one or more of thepulmonary veins rather than at the SA node. These atrial arrhythmiashave been treated by a variety of methods including pharmocologictreatments, highly invasive surgical procedures and linear andcircumferential RF ablations of the myocardial wall. However, each ofthese methods has drawbacks, e.g., the pain and extended recovery timefor invasive surgery, relative ineffectiveness of pharmacologictreatments and restenosis at the ablation site due to the application ofRF energy or other heat based therapies thereto.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a method and apparatus forablating tissue within a patient comprising inserting into a patient'svenous system a substantially rigid sheath, piercing a desired point ofpenetration in the patient's interatrial septum to pass the rigid sheaththrough the interatrial septum into the patient's left atrium,maneuvering a flexible section mounted on the rigid sheath into aposition in which a distal end of the flexible section is locatedadjacent to a portion of tissue to be ablated, the flexible sectionincluding an occluding structure which has a retracted position andextended position, and passing an ablation catheter through the flexiblesection so that an ablation tip of the ablation catheter is adjacent tothe portion of tissue to be ablated.

BRIEF DESCRIPTION OF DRAWINGS

[0007]FIG. 1 shows a partially cross-sectional side view of a deviceaccording to the present invention;

[0008]FIG. 2 shows a cross-sectional view of the device of FIG. 1, takenalong line 2-2;

[0009]FIG. 3 shows a view of the device in position within the rightatrium of a patient with a distal tip of a dilator adjacent to theforamen ovale;

[0010]FIG. 4 shows a side view of the device of FIG. 1 in position witha needle penetrating the foramen ovale of a patient;

[0011]FIG. 5 shows a side view of the device of FIG. 1 in position witha dilator penetrating the opening in the foramen ovale made by theneedle of FIG. 4;

[0012]FIG. 6 shows a side view of the device of FIG. 1 in positionwithin a pulmonary vein;

[0013]FIG. 7 shows a side view of the device of FIG. 1 in positionwithin the pulmonary vein with an occluding balloon inflated;

[0014]FIG. 8 shows the depth markers of the catheter according tocertain embodiments of the invention;

[0015]FIG. 9 shows a cross section of the left atrium and pulmonary veinillustrating the extended atrial tissue;

[0016]FIG. 10 shows a side view of a device according to an alternateembodiment of the invention;

[0017]FIG. 11 shows a side view of a collection of pre-shaped rigidsheaths for use with an embodiment of the invention.

DETAILED DESCRIPTION

[0018] The present invention may be further understood with reference tothe following description and the appended drawings, wherein likeelements are provided with the same reference numerals.

[0019] When arrhythmia resulting from the origination of contractioninitiating signals within one or more of the pulmonary veins rather thanat the SA node is detected, known techniques may be used to locate thepoint of origination and the path of conduction. After this data hasbeen obtained, the device and method according to the present inventionallows a user to ablate a portion of the identified pulmonary vein nearthe orifice or collar of the pulmonary vein to create a circumferentialconduction block preventing these improper contraction originationsignals from propagating into the left atrium and restoring a normalsequence of contractions.

[0020] As shown in FIG. 1, the device 10 may include a flexible section12 which is flexible laterally but is axially stiff so that it may bepushed distally to seal the orifice as will be described below. Theflexible section 12 according to this embodiment of the invention may beformed as a sheath extending from a proximal end (not shown) whichremains outside a patient's body to a distal end 14 which, when thedevice 10 is in an operative position is located within the patient'sbody. As shown in FIG. 2, the flexible section 12 includes a centrallumen 16 extending therethrough from the proximal end to the distal end14. As shown in FIGS. 1 and 2, an annular balloon 18 is mounted to theflexible section 12 adjacent to the distal end 14 and is coupled to aninflation lumen 20 extending along the outside of the flexible section12 from the proximal end to the distal end 14 at which the inflationlumen 20 is fluidly coupled to the balloon 18. Alternatively, inflationlumen 20 may extend internally along the device. A rigid sheath 22 isslidably received within the flexible section 12. Alternatively, theflexible section 12 may simply consist of a flexible sheath 12′extending from a distal end of the rigid sheath 22 as described below inregard to FIG. 10.

[0021] The rigid sheath 22 may have a predetermined shape selected toaid in the insertion of the device 10 into the left atrium (LA) via atranseptal puncture and an approach from the inferior vena cava into theright atrium (RA) as will be described in more detail below.Specifically, the rigid sheath 22 may preferably have an outer diameterof between 9 and 14 French, more preferably approximately 11 French.Those skilled in the art will understand that an outer diameter of theflexible section 12 will be slightly larger than that of the rigidsheath 22, while the ablation catheter 24 will have an outer diameterslightly smaller than that of the rigid sheath 22. For example, anablation catheter 24 with an outer diameter of 10 French may be slidablyreceived within a rigid sheath 22 having an outer diameter of 11 Frenchwith an flexible section 12 having an 11.5 French outer diameter.

[0022] An ablation catheter 24 is slidably received within a centrallumen of the rigid sheath 22 so that the ablation catheter 24 may beadvanced distally beyond a distal end of the rigid sheath 22 to anextended position in which a cryogenic tip 26 mounted at a distal end ofthe ablation catheter 24 extends distally beyond a distal end of theflexible section 12. The ablation catheter 24 and the cryogenic tip 26may, for example, be constructed in accord with the teaching of any ofthe '657, 104 and '595 patents. Specifically, the ablation catheter 24may include a high pressure refrigerant lumen 25 extending through theablation catheter 24 to a Joule-Thomson expansion element, e.g., acapillary tube, which opens into an expansion chamber formed within thecryogenic tip 26. Furthermore, the ablation catheter 26 may include oneor more electrodes as described in the '657 patent which may be used tolocate and map the site of the origin of the improper contractionorigination signals.

[0023] In one embodiment, the catheter 24 may be a cryosurgical catheterthat uses a two stage Joule-Thompson cooling system. A first loop, whichmay be closed or open, may extend into the tip of catheter 24. Thisfirst open loop may be pre-cooled by a second loop, which may be closedor open, whereby at least the high pressure portion of the first loopand the low pressure portion of the second loop are placed in a heatexchange relationship. In certain embodiments, the fluid circulating inthe first loop may be a mixed gas refrigerant. The mixed gas refrigerantmay include a hydrocarbon. As another example, the refrigerant in thefirst loop may be nitrous oxide.

[0024] Furthermore, in certain embodiments of the invention, thecatheter 24 may be deflectable. That is, the catheter tip may bedeflectable via a deflection mechanism associated with the catheterhandle. In use, the deflectable section of the catheter will begenerally within or extending from the flexible section 12. Thiscombination of the deflectable catheter and flexible section may allowthe device 10 to more easily be positioned in the desired pulmonaryvein, as explained below.

[0025] When a user (e.g., an electro-physiologist or EP) has previouslydetermined that contraction origination signals are improperlyoriginating from a site within one of the pulmonary veins (PV), using,for example, electro-physiology (EP study) the device 10 is insertedinto the LA of the patient using the Seldinger technique as is known tothose skilled in the art as follows. Of course, those skilled in the artwill understand that, where an EP study has not previously beenperformed, an EP mapping catheter may be inserted into the LA via therigid sheath 22 of the device 10.

[0026] Specifically, a guide wire (not shown) is inserted into the RAthrough the inferior vena cava. The rigid sheath 22 is inserted into theflexible section 12 and is then advanced along the guide wire until adistal end of the rigid sheath enters the RA via the inferior vena cava,as shown in FIG. 3. Further advancing the rigid sheath 22 and theflexible section 12 distally along the guide wire will advance the bentsection of the rigid sheath 22 toward the point at which the inferiorvena cava enters the RA. The bend in the rigid sheath 22 is selected sothat, at this point, a distal end of the rigid sheath 22 is pointedsubstantially toward a position on the interatrial septum at which theforamen ovale (FO) is located. The dimensions of the rigid sheath 22 arealso selected so that, at this point, the distal end of the rigid sheath22 is positioned adjacent to the FO. The curvature of the rigid sheath22 may preferably be between 30 and 90 degrees depending on the anatomyof the patient, and in one embodiment a 60 degree curvature is used.

[0027] As shown in FIGS. 3 and 4, a dilator 28 with a Brouchenboroghneedle 30 received therein is then inserted through a central lumen 23of the rigid sheath 22 until a distal end of the dilator 28 extendsbeyond a distal end of the rigid sheath 22. The user may then probe theinterartial septum noting the relative strength of various locations onthe interatrial septum until the precise location of the FO isdetermined (i.e., the FO forms a soft apical spot on the septum). Thoseskilled in the art will understand that intracardiac ultrasound may alsobe used to assist in locating the FO. Then the Brouchenborogh needle 30is extended from the distal end of the dilator 28 to pierce the FOforming a transeptal puncture (TP) extending into the LA as shown inFIG. 4. The dilator 28 is then advanced through the TP in theinteratrial septum to expand a diameter of the TP as shown in FIG. 5.

[0028] Thereafter, the Brouchenborogh needle 30 is retracted into thedilator 28 and removed from the body. The rigid sheath 22 is thenadvanced along the dilator 28 to pass through the TP into the LA. Theflexible section 12 is then pushed along the rigid sheath 22 (utilizingthe longitudinal rigidity of the flexible section 12) until a distal endof the flexible section 12 extends through the opening in theinteratrial septum into the LA as shown in FIG. 6.

[0029] The ablation catheter 24 is then advanced distally through therigid sheath 22 until the cryogenic tip 26 extends distally beyond thedistal end of the rigid sheath 22 and the distal end of the flexiblesection 12. At this point there are several known techniques formaneuvering a catheter to a desired position within the opening of theone of the PV's from which the contraction origination signals areimproperly originating. In certain embodiments, the catheter 24 isdeflectable via a deflection mechanism associated with the catheterhandle, which may ease the positioning of the catheter. Furthermore, byadvancing the rigid sheath 22 further into the LA, the bend in the rigidsheath may be employed to assist in aiming the cryogenic tip 26 towardthe desired PV opening. After the cryogenic tip 26 has been properlypositioned well within the PV, the flexible section 12 is advanceddistally along the ablation catheter 24 until the distal end of theflexible section is near the orifice at which the PV opens into the LA.To aid in ensuring proper positioning of the cryogenic tip 26 and theflexible section 12 in the orifice of the PV, the flexible section 12and the rigid sheath 22 include radiopaque markers at the respectivedistal ends thereof or other desired locations.

[0030] Once the flexible section 12 has been positioned near the openingto the PV, the user may inject radiopaque dye into the PV via theflexible section 12 with the radiopaque fluid exiting the flexiblesection 12 via openings 36 located distally of the balloon 18. This maybe done so as to aid in locating, under imaging, the orifice of the PV.The user may then inflate the balloon 18 by coupling a source ofinflation fluid (not shown) to a proximal end of the inflation lumen 20.In one embodiment, the inflation fluid may be a diluted radiopaque orcontrast fluid such that the balloon may more easily be seen underimaging. The flexible section 12 is then advanced until the balloon 18is seated on the orifice of the PV, thereby occluding the flow of bloodfrom the PV into the LA as shown in FIG. 7. The description herein of aballoon does not imply that blood flow must be occluded by an inflatablecuff. Rather, any structure which is radially extendible from the sheath12 to occlude blood flow therepast will serve the purposes of thisinvention. There are many alternative constructions for this structure,which will be known to those skilled in the art.

[0031] The ablation catheter 24 is then retracted from the PV so thatthe distal end of the ablation catheter is positioned slightly beyondthe distal end of the flexible section 12 at the orifice of the PV. Asshown in FIG. 8, depth markings 31 may be provided on the shaft ofcatheter 24 adjacent catheter handle 27. The depth markings 31 may beused to determine the relative positions of the distal ends of theflexible section 12 and ablation catheter 24. This allows the user tomore precisely determine the distance that the catheter tip 26 extendsin the PV.

[0032] In certain embodiments of the invention, the user may wish topreferably ablate tissue in the extended atrial tissue zone of the PV.As shown in FIG. 9, in the transition region between the left atrium andPV, atrial tissue extends into the PV for about 1-2 cm.

[0033] At least two advantages may be obtained by making the ablation inthe extended atrial tissue. First, if the ablation is made deeper in thePV and not in the extended atrial tissue, it is believed that in somecases the contraction initiating signal, which originates in the PV,will find a new path, which bypasses the ablated tissue, and resumes thearrhythmia. It is believed that this bypass problem will not occur orwill be less frequent when the ablation has been performed in theextended atrial tissue. Second, it is believed that restenosis is morecommon if the ablation is made more deep in the PV (i.e., in the venoustissue) than if the ablation is made in the extended atrial tissue.

[0034] Accordingly, in certain embodiments, once desired catheter tiplocation has been confirmed, the ablation of tissue may be initiated.

[0035] The user supplies a cryogenic fluid to an expansion chamberformed in the cryogenic tip 26 via the cooling fluid lumen 25 to lowerthe temperature of the cryogenic tip 26 so that an ice ball forms aroundthe tip. Because blood flow from the PV into the LA is substantiallyimpeded by the balloon 18, warming of the cryogenic tip 26 by the flowof blood past the cryogenic tip 26 is minimized and the formation of alarge frozen tissue mass or ice ball is facilitated. The ice ball formedmay be large enough that it contacts the entire circumference of theinner wall of the PV ablating the tissue and forming a circumferentialconduction block between the LA and the site of origination of theimproper contraction originating signals.

[0036] It may not be desirable to move the cryogenic tip while an iceball is formed therearound as this ice ball may adhere to tissue andcause damage when moved. If the ice ball formed is not large enough toimmediately form a completely circumferential conduction block, the usermay ablate a first portion of tissue with a first ice ball and then thawthis first ice ball. The user may reposition the cryogenic tip adjacentto a second portion of tissue to be ablated and form a second ice ball,repeating this process until the entire desired portion of tissue hasbeen ablated thereby forming the circumferential conduction block.

[0037] In addition, a user may stun tissue by applying the cryogenic tip26 thereto at a temperature warmer or for a duration shorter than thatrequired to ablate the tissue. Changes in the path of conduction of thecontraction origination signals may then be electrically monitored tofurther locate the site of origin. A user may also utilize theelectrodes at the distal end of the ablation catheter 24 to apply anelectric charge to one side of the circumferential conduction blockwhile monitoring the state of the opposite side thereof to determinewhether the tissue has been ablated sufficiently to create the desiredconduction block.

[0038]FIG. 10 shows a device according to an alternate embodiment of theinvention wherein a device 10′ includes a flexible section 12′ formed asa tube extending distally from the distal end of the rigid sheath 22′.The flexible section 12′ is coupled to the distal end of the rigidsheath 22′ and is preferably not slidable relative thereto. Sections 12′and 22′ may be heat fused together.

[0039] Accordingly, a single sheath may be formed with a flexiblesection 12′ and a rigid section 22.′ The inflation lumen 20′, which isformed on an outer surface of the sheath extends from an inflation port52′ to balloon 18′. Alternatively, inflation lumen 20′ may extend alongthe interior of the sheath. An ablation catheter 24 as described abovein regard to the device 10 is then slidably received through the sheath.In other respects, the device 10′may be constructed in accord with thedescription of the device 10 above. Ablation catheter 24 may be insertedinto the sheath via hemostasis valve 50, which may have a side port 54and 3-way stopper 56 associated therewith.

[0040] Once the device 10′ has been inserted into the LA of the patientusing the Seldinger technique, the ablation catheter 24 is advanceddistally through the rigid section 22′ and the flexible section 12′until the cryogenic tip 26 extends distally beyond the distal end of theflexible section 12′ and is maneuvered so that the cryogenic tip 26 iswithin the opening of the one of the PV's from which the contractionorigination signals are improperly originating. The balloon 18′ is theninflated and the rigid section 22′ and the flexible section 12′ are thenadvanced distally along the ablation catheter 24 until the balloon 18′is seated in the orifice at which the PV opens into the LA. As with thedevice 10, to ensure proper positioning of the cryogenic tip 26, aradiopaque marker 34′ is provided adjacent balloon 18′. In addition,radiopaque fluid may be injected into the PV via the opening 36′.

[0041] Once the desired position of the ablation catheter 26 has beenconfirmed, the ablation of tissue may be initiated as described above inregard to the device 10.

[0042] Another embodiment of the invention is shown in FIG. 11. In thisembodiment, instead of providing a flexible section 12, a plurality ofgenerally rigid sheaths 200, 210, 220 and 230 are provided with variousdegrees of curvature. While only four sheaths are shown more or less maybe provided so as to accommodate various degrees of curvature, e.g.,from straight to 180 degrees of curvature. Depending on the patient'sanatomy and the particular PV to be treated, the user would select thedesired sheath to aid in placement of the catheter and balloon.

[0043] In the preceding specification, the present invention has beendescribed with reference to specific exemplary embodiments thereof. Itwill, however, be evident that various modifications and changes may bemade thereto without departing from the broadest spirit and scope of thepresent invention as set forth in the claims that follow. Thespecification and drawings are accordingly to be regarded in anillustrative rather than restrictive sense. For example, while theinvention has been described for use with PV ablation, the device may beused in other parts of the vasculature.

1-27. (Canceled)
 28. A method of ablating tissue within a patientcomprising the steps of: inserting into a patient a substantially rigidsheath; maneuvering a flexible section mounted on the rigid sheath intoan operative position in which a distal end of the flexible section islocated within one of a pulmonary vein and a pulmonary vein ostiumadjacent to a portion of tissue to be ablated, the flexible sectionincluding an occluding structure which has a retracted position andextended position; extending the occluding structure to the extendedposition once the flexible section is in the operative position to blockblood flow past the occluding structure; and passing an ablationcatheter through the flexible section so that an ablation tip of theablation catheter exits the flexible section adjacent to the portion oftissue to be ablated.
 29. The method according to claim 28, wherein theportion of tissue to be ablated is extended atrial tissue.
 30. Themethod according to claim 28, further comprising the step of cooling theablation tip to cryogenically ablate the portion of tissue to beablated.
 31. The method according to claim 30, wherein an interior ofthe ablation tip forms an expansion chamber fluidly coupled to a sourceof high-pressure refrigerant.
 32. The method according to claim 28,wherein the flexible section is longitudinally rigid and axiallyflexible, the flexible section being slidably mounted on the rigidsheath so that, in a first position, a distal end of the flexiblesection is located proximal to the distal end of the rigid sheath and,in a second position, the distal end of the flexible section is locateddistal of the distal end of the rigid sheath.
 33. The method accordingto claim 28, wherein the flexible section is longitudinally rigid andaxially flexible, a proximal end of the flexible section being mountedto the distal end of the rigid sheath so that a distal end of theflexible section extends distally from the distal end of the rigidsheath.
 34. The method according to claim 28, wherein the occludingstructure includes a balloon coupled to a source of inflation fluid viaan inflation lumen extending to an inflation opening which, when theoccluding structure is positioned within the body of a patient, remainsoutside the body.
 35. The method according to claim 28, wherein theportion of tissue to be ablated extends continuously around acircumference of the one of the pulmonary vein and the pulmonary veinostium so that ablation of this portion of tissue forms a conductionblock to prevent transmission of contraction originating signals fromwithin the pulmonary vein to the heart.
 36. The method according toclaim 28, wherein the rigid sheath includes a radiopaque marker at adistal end thereof to assist in visually positioning the guide sheath.37. The method according to claim, wherein the flexible section includesa dye opening adjacent to the distal end thereof, the dye opening beingoperatively associated with a dye source that remains outside the body,the method further comprising the step of injecting, after the occludingstructure has been radially extended, a radiopaque dye into thepulmonary vein via the dye opening in order to confirm the position ofthe flexible section or occlusion structure.
 38. The method according toclaim 37, wherein the flexible section includes a dye opening adjacentto the distal end thereof, the dye opening being operatively associatedwith a dye source that remains outside the body, the method furthercomprising the step of injecting, after the occluding structure has beenmoved to the extended position, a radiopaque dye into the pulmonary veinvia the dye opening in order to aid in imaging the pulmonary vein. 39.The method according to claim 28, further comprising the step of movingthe ablation tip circumferentially around an inner surface of apulmonary vein of the patient to create a circumferential conductionblock therein to block transmission of contraction originating signalsfrom the pulmonary vein into the patient's heart.
 40. The methodaccording to claim 28, wherein the rigid sheath includes a curvedsection, and when the guide sheath is inserted into the venous systemthe curved section extends from the inferior vena cava into the rightatrium such that the distal end of the rigid sheath is directed towardan approximate location of a desired point of penetration in thepatient's interatrial septum.
 41. A system for ablating tissuecomprising: a guide sheath having a curved section dimensioned so that,when the guide sheath extends from a right atrium of a patient throughan interatrial septum to a left atrium, a distal end of the guide sheathmay be rotated to face a pulmonary vein ostium laterally spaced from anaxis of a portion of the sheath extending through the interatrialseptum; an axially flexible section mounted on the sheath; an occludingstructure mounted on a distal end of the axially flexible sheath, theoccluding structure having an extended configuration for blocking a flowof blood therepast and a retracted configuration; and an ablationcatheter including an ablation tip at a distal end thereof, the ablationcatheter being slidably mounted within the sheath and the axiallyflexible section so that the ablation tip may be moved from a firstposition in which the ablation tip is received within the sheath to asecond position in which the ablation tip is extended therefrom.
 42. Thesystem according to claim 41, wherein an interior of the ablation tipforms an expansion chamber coupled to a source of high-pressurerefrigerant.
 43. The system according to claim 41, wherein the axiallyflexible section is slidably received around an outer surface of thesheath so that the distal end of the axially flexible section may bemoved between a first position in which the distal end of the axiallyflexible section is located proximally of the distal end of the sheathand a second position in which the distal end of the axially flexiblesection is located distally of the distal end of the sheath.
 44. Thesystem according to claim 41, wherein a proximal end of the axiallyflexible section is coupled to the distal end of the sheath.
 45. Thesystem according to claim 41, wherein the occluding structure includes aballoon coupled to a source of inflation fluid.
 46. The system accordingto claim 41, wherein the ablation catheter is cryogenic.
 47. A method ofablating tissue within one of a pulmonary vein and a pulmonary veinostium comprising the steps of: inserting into a patient's left atrium asheath; sliding an axially flexible section over the sheath into anoperative position in which a distal end of the axially flexible sectionis located adjacent to a portion of tissue to be ablated, the axiallyflexible section including an occluding structure which has a retractedposition and an extended position; passing an ablation catheter throughthe axially flexible section so that an ablation tip of the ablationcatheter is adjacent to the portion of tissue to be ablated; andextending the occluding structure to the extended position once theaxially flexible section is in the operative position to block bloodflow through the pulmonary vein past the portion of tissue to beablated.
 48. The method according to claim 47, wherein the axiallyflexible section is longitudinally rigid.
 49. The method according toclaim 47, wherein the axially flexible section includes a dye openingadjacent to the distal end thereof, the dye opening being operativelyassociated with a dye source that remains outside the body, the methodfurther comprising the step of injecting, after extending the occludingstructure, a radiopaque dye into the pulmonary vein via the dye openingto confirm the position of one of the flexible section and the occlusionstructure.
 50. A system for ablating tissue within a pulmonary veincomprising: a guide sheath having a curved section dimensioned so that,when the guide sheath extends from a right atrium of a patient throughan interatrial septum to a left atrium, a distal end of the guide sheathmay be rotated to face an opening into a pulmonary vein laterally spacedfrom an axis of a portion of the guide sheath extending through theinteratrial septum; an axially flexible section including an occludingstructure mounted to a distal end thereof, the occluding structurehaving an extended configuration for blocking a flow of blood therepastand a retracted configuration; and an ablation catheter including anablation tip at a distal end thereof, the ablation catheter beingslidably mounted within the guide sheath and the axially flexiblesection so that the ablation tip may be moved from a first position inwhich the ablation tip is received within the guide sheath to a secondposition in which the ablation tip is extended distally from a distalend thereof.